Studies on serodiagnosis, epidemiology and management of sunflower necrosis viral disease in Northern karnataka
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Date
2006
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UAS Dharwad
Abstract
Sunflower necrosis is a major virus disease of sunflower caused by Tobacco Streak
Virus. It was first reported from Kolar district of Karnataka State during 1997. The roving
survey for disease incidence in Northern Karnataka was undertaken and disease map was
developed, which revealed the presence of disease in all the three seasons. The disease was
severe in Bijapur, Raichur and Koppal districts showing 15-20 per cent incidence. Infected
plants showed mosaic, marginal necrosis and malformation of leaves, calyx and earhead,
early infected plants showed partial seed filling. TSV -S had wide host range and its Thermal
Inactivation Point was 45°C, Dilution End Point 10-4 and Longevity in vitro of 8 h. The
epidemiological studies indicated positive correlation of disease with thrips population and
also with maximum temperature.
The virus was purified by extraction in Phosphate buffer, PEG precipitation, density
gradient centrifugation and ultra centrifugation. Electron microscopic observations revealed
isometric shaped particles in decoration method. Immunizing rabbit with purified TSV -S
produced the antiserum. SDS-P AGE revealed 30 Kda Protein band when stained with
coomassie brillant blue. Direct Antigen Coating Enzyme Linked Immuno Sorbant Assay
indicated presence of virus particles in samples of sunflower, cowpea, peas, green gram,
tomato, soybean, black gram and red gram but not in seeds of diseased plant. In
Immunodiffusion test precipitation line appeared around wells containing diseased samples.
RT-PCR yielded 800 bp length coat protein gene.
The disease had a drastic effect on yield parameters of sunflower. Germplasm lines
GMU-209, GMU-244, GMU-249, and GMU-259 exhibited some degree of tolerance
properties with less than 10 per cent disease incidence. Crop could be protected from heavy
loss due to virus infection by Imidacloprid seed treatment (@ 5 g/kg) + spray (@ 0.25 ml) at
30, 45 and 60 days after sowing and sorghum as border crop.